1. Field of the Invention
This invention relates in general to hard disk drives, and more particularly, to a system for etching and lubrication of swage balls used in the DASD suspension-arm attachment swaging process of head stack assembly (HSA).
2. Description of Related Art
Moving magnetic storage devices, especially magnetic disk drives, are the memory device of choice. This is due to their expanded non-volatile memory storage capability together with a relatively low cost. Accurate retrieval of the stored information from these devices becomes critical, requiring the magnetic transducer to be positioned as close to the storage media as possible. Optimally, the transducer may actually contact the media.
Magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk having concentric data tracks defined for storing data, a read/write transducer for reading data from and/or writing data to the various data tracks, a slider for supporting the transducer adjacent the data tracks typically in a flying mode above the storage media, a suspension assembly for resiliently supporting the slider and the transducer over the data tracks, and a positioning actuator coupled to the transducer/slider/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track center line during a read or a write operation. The transducer is attached to or is formed integrally with the slider which supports the transducer above the data surface of the storage disk by a cushion of air, referred to as an air bearing, generated by the rotating disk. The transducer/slider/suspension assembly is often referred to as the head gimbal assembly (HGA).
Alternatively, the transducer may operate in contact with the surface of the disk. Thus, the suspension provides desired slider loading and dimensional stability between the slider and an actuator arm which couples the transducer/slider/suspension assembly to the actuator. The suspension is required to maintain the transducer and the slider adjacent the data surface of the disk with as low a loading force as possible. The actuator positions the transducer over the correct track according to the data desired on a read operation or to the correct track for placement of the data during a write operation. The actuator, either rotary or linear, is controlled to position the transducer over the desired data trap by shifting the combination assembly across the surface of the disk in a direction generally transverse to the data tracks.
Currently, ball swaging is the preferred method of attachment of the head suspension assembly to the actuator arm. Swaging is a process for connection where the wall thickness of a thin wall tubular component is expanded against a thick wall component by plastic deformation. More specifically, it is a process used in connecting a suspension to an actuator in a hard disk drive. The process of swaging involves pressing and fastening the periphery of a boss to the inner face of a through-hole in an actuator arm. The boss is formed in a mount plate or mount block of the transducer suspension. The boss is inserted into the through-hole formed in the actuator arm. Then, a ball of a little larger size than the inner diameter of the opening of the boss is passed through. The swaging process generally provides a stronger joint than a press fit, because the thin-wall member is work hardened by the deformation process, which increases tensile strength. Examples of swaging technology include the HTI interlock swage, the Seagate tandem swage and the IBM thin back-to-back swage.
In order for swaging to be effective, swage balls need to be lubricated. The lubricant prevents development of high swage forces which can lead to particle generation by galling, and to product deformation as well. A popular solid film lubricant used for this purpose is tungsten disulfide, which provides excellent lubricity but is a significant source of particulate and smear type contamination in disk drives. In addition, the steel balls typically need to be roughened by methods such as abrasive blasting with aluminum oxide (alumina) in order for the solid lubricant to adhere strongly enough. Residual alumina is another form of unacceptable particulate contamination in hard disk drives, particularly those with MR heads.
Accordingly, it can be seen that there is a need for a new process and solution for preparing the balls used for the swaging of transducer suspensions to actuators for use in hard disk drives.